The present invention relates to a laser beam machine for executing cutting machining on a workpiece in the shape of a plate.
FIG. 7 is a view showing how to cut a corner portion according to a conventional machining method wherein (a) is a view showing loop R of movement path, and (b) is a view showing a part of a machining program.
In order to cut a sharp corner formed by crossing straight lines of cut paths with a laser beam machine in a conventional method, for instance, in order to cut a sharp corner formed by crossing cut paths L1 and L5 (full line), which are straight lines, at position P1 (x coordinate is 0, y-axis coordinate is 0) as shown in FIG. 7(a), cut path L1 is cut in an arrow direction as shown in FIG. 7(a), and thereafter, the sharp corner is cut, circling outside the cut shape along loop R (LR) as shown by a broken line, passing through positions P1, P100 (x coordinate is 5, y-axis coordinate is 0), P101(x coordinate is 0, y-axis coordinate is 5) in order, without immediately cutting cut path L5. This method is adopted in order to prevent the sharp corner from not being cut in a desired shape for the reason that a workpiece 70 is overheated with laser beam so as to be melted when feed speed F temporarily becomes zero at the time of passing through position P1 by the torch. This machining method is executed by a machining program PRO which is comprised of a plurality of machining steps PS1, PS2, . . . , as shown in FIG. 7(b). In the machining program PRO, a loop R program LRP for circling on the above-mentioned loop R (LR) is inserted between machining steps PS, PS5.
That is, linear interpolation instruction (G01) where feeding speed F is 30,000 mm/min, and end point is position PI is instructed in block N1 of the first machining step PS1 of the top in the figure, and linear interpolation instruction (G01) of moving 50 mm in a negative direction of y-axis from position P1 is instructed in block N5 of the fifth machining step PS5 of the bottom. And, the above-mentioned loop R program LRP is inserted before block N5.
The loop R program LRP is comprised of three blocks N2, N3, and N4 of machining steps PS2, PS3 and PS4, as shown in FIG. 7(b). In the first block N2, linear interpolation instruction (G01) of moving 5 mm in a positive direction of x-axis along movement path S1 to end position P100 in order to elongate cut path L1, maintaining the feeding speed F, is instructed. When a torch reaches position P100, arc interpolation instruction (G03) of arc R1, connecting with both extended lines of cut paths L1 and L5, having 5 mm of radius R determined on the basis of a predetermined acceleration by which the feed speed F can be maintained, is instructed in the second block N3. When the torch reaches position P101, linear interpolation instruction (G01) of moving 5 mm in a negative direction of y-axis along movement path S2 to end position P1 in order to elongate cut path L5, maintaining the feeding speed F, is instructed in the last block N4. When returns to position P1, the loop R program LRP finishes, and linear interpolation instruction (G01) of moving 50 mm in a negative direction of y-axis is instructed in block N5 of machining step PS5, so as to continue cutting machining along cut shape of cut path L5, maintaining feed speed in cut path L1.
The torch moves along the loop R (LR) comprised of straight line S1, arc R1 and straight line S2, so that cutting machining is possible at the same feed speed F at any position in a cut shape, irrespective of a sharp corner. Therefore, the workpiece 70 can be cut in a desired cut shape by cutting a sharp corner, maintaining a good cut face having no machining irregularity.
In the above-mentioned machining method, it is necessary to move the torch along a movement path which is comprise of a straight line, an arc and a straight line every machining on the sharp corner, so that the time for circling on the movement path at a predetermined feed speed prevents speedy machining. In case where there are many sharp corners to be machined, such as a case where parts having a sharp corner in great number are located on the workpiece 70 (nesting), or such a case where parts to be cut have many sharp corners, the machining efficiency is lowered owing to increased number of circling, and it is further difficult to actualize speedy machining thereby.
Furthermore, it is necessary to insert the loop R program LRP having three blocks according to a straight line, an arc and a straight line every machining block of the sharp corner when producing a machining program. Therefore, longer time is necessary for such insertion, and more specifically, much work is necessary in case where many sharp corners are machined. Besides, program capacity for the loop R program LRP is also necessary according to the number of the sharp corner. More inconveniently, bigger locus of loop R to be inserted into a corner leads to meaningless cutting of a material, and nesting efficiency is lowered thereby.
Under these circumstances, the development of the laser beam machine for cutting a sharp corner on the basis of a desired cut shape, maintaining a good cut face having no machining irregularity, capable of actualizing speedy cutting machining in an easy way, has been desired.
A laser beam machine of the invention has:
a radiating means for radiating laser beam on a workpiece to be cut;
a means for moving and driving, for moving and driving the radiating means at predetermined feed speed;
a machining execution means for moving and driving the radiating means through the means for moving and driving on the basis of a movement instruction instructed by a machining program;
a sharp corner judgment means for judging as to whether a corner of cut shape in the workpiece is a sharp corner or not on the basis of the machining program;
additional locus producing means for producing sharp corner, for producing additional locus for producing sharp corner when machining a corner which is judged as the sharp corner by the sharp corner judgment means; and
a sharp corner machining execution means for machining the corner judged as the sharp corner on the basis of the additional locus for producing sharp corner produced by the additional locus producing means for producing sharp corner.
According to an aspect of the invention, an additional locus for producing sharp corner is automatically produced when machining on a corner judged as a sharp corner, and the corner is machined on the basis of the additional locus for producing sharp corner. Therefore, the sharp corner can be easily machined, maintaining a good cut face having no machining irregularity without spending longer time for programming for machining. More specifically, in case where there are many sharp corners to be machined, producing of machining program can be further lightened. Besides, more conveniently, it is not necessary to increase program capacity for machining on the sharp corner.
According to an another aspect of the invention, the sharp corner machining execution means can control feed speed of the radiating means so as to move the radiating means, decelerating feed speed from the feed speed before entering into the sharp corner, from passing of the corner till returning to the corner by the radiating means.
In this case, the additional locus for producing sharp corner shorter than a conventional locus can be produced when machining on the sharp corner since the torch moves, reducing feed speed from passage of laser beam on a corner judged as the sharp corner till return to the corner. Then, speedy machining can be realized, maintaining a good cut face having no machining irregularity. In case where there are many sharp corners to be machined, more speedy machining is possible. Besides, meaningless cutting of a material is saved by shortening the locus so as to improve nesting efficiency.
According to an another aspect of the invention, a sharp corner machining execution judgment means for judging as to whether a machining execution instruction of the sharp corner is instructed in the machining program or not is provided, whereby machining on the corner is executed by the sharp corner machining execution means when the sharp corner machining execution judgment means judges that the machining execution instruction of the sharp corner is instructed in the machining program.
In this case, as to whether sharp corner machining is instructed in a machining program or not is judged, and the corner is machined on the basis of the additional locus for producing sharp corner when the judgment is that the execution instruction is instructed. Then, an operator can freely select one of two options, that is, an operator executes automatic machining on the sharp corner using the additional locus producing means for producing sharp corner, or manually inserts a machining block in the machining program in a conventional way, so that the machining contents can be made flexible.
According to an another aspect of the invention, a laser beam radiation control means for controlling radiation of the laser beam on the workpiece from the radiating means is provided, whereby no laser beam is radiated on the workpiece through the radiating means by the laser beam radiation control means while the sharp corner machining execution means moves and drives the radiating means along the additional locus for producing sharp corner.
In this case, no laser beam is radiated on the workpiece during movement of the moving means along the additional locus for producing sharp corner, so that meaningless cutting of a material can be saved and nesting efficiency can be improved thereby.